Motor fuel



Patented June 10, 1952 Moron FUEL AllenR. Jones, Roselle, and John'O. Smith, In,

*N. J., 'ass'ignors -'to "Standard Oil Development Company, a corporation for Delaware 1N0 Drawing. appucancngmne 1,1950, serial No. 165,;60

4 Claims. (Cl. '44...70.)

The present invention relates to a motorf-uel composition adapted to provide distinct improved motor operation under cool moist operating conditions. The motor fuel composition-of the present invention comprises a hydrocarbon mixture boiling in "the gasoline boiling range-which contai-ns-as an ingredient a very small-percentage of an aliphatic thioether of a mono-carb'oxylicacid. In addition, the fuel compositions "of the present invention may contain'solvent-oiland'other"additives such as lead alkyl 'antidetonants, dyes, gum inhibitors, oxidation inhibitors, and the like.

The novel motor fuel compositions'of this invention are primarily intended to overcomecertain operational difiiculties in connection with automotive, marine, stationary, and "airplane engines. The difiiculties referred to result in frequent stalling of the engine under idling conditions. This stalling maybe "encountered 'whenever the weather conditions in which the engine is used are such' as t'o'provide' a relatively high humidity, and a temperature below'ab0ut60" F.

While this problem has actually "been'existent for many years, attention has recently been 'focused on it due to numerous complaints of car owners particularly in the northern portion of the United States. These owners 'leport that during 0001, wet weather their cars jgive poor idling performance characterized by a high number of'engine'stalls. "Thedifliculty is encountered in an types of cars employing all types 'of carburetors and utilizing all commercial brands of gasoline.

Inorder "to indicate the magnitude of this 'dilficulty, reference may be made to a survey conducted in the New Jerseyarea based on the experiences of 300 car owners drivingtwentydiflerent car models, during the fall iandwinteriperi'od. 'I-hese cars employed the winter grade of regular and premium commercial 'gasolin'es. Table I gives a summary of "the results -"obtained, showing the substantial number'of stalls encountered in the operation of the cars under 'the indicated conditions.

TABLE I Number of Complaints of Two Stalls or More (per. 100 Cars) The bare statistics-of TableI coupled wit-h the common experience "of all automotive users serves to indicate themag-nitude of-the problem ofengine stalling encountered under-cool, humid -temperatureconditions. However, it is-significant to note that this problem has of latebecome of increased importance due to certain specific factors. first, most post wa-rcars are-now provided without a manual throttle so that car owners are no longer able'to-increase the idle speed during the warm-up period to prevent stalling. Second, the idlespeed-of cars with automatic transmissions is rather-critical-during a, warm-up andthe fastest idle which be used must not be too fast, increasing the criticality 'of stalling conditions. Third, 'stalling'of a car 'with automatic transmission frequently does not occur until the driver'isready to accelerate, so that just at this most inconvenient time it is necessary-to shift the car to neutral, restart the engine, and shift back into gear; magnifying the inconvenience of frequent stalls. A fourth factor'affecting'the magnitude of stalling difficulties relates'to the volatility of the fuels now provided for automoti-ve use. The-volatility of commercial fuels over a period of years has'been increased sufiiciei'ltly to increasestalling difficulties as will be brought outherein.

On investigating this problem-it has "been determined that the cause ofrepe'atedenginesta-lling'in'cool, humid weatheris the formation-of ice in thecarburetor of the engine. Ona'cool, moist day, gasoline evaporating in the carburetor exerts sufiicient refrigerating 'eifect to condense "and freeze -moisture present-in the air entering the carburetor. 'Normal'fuel vaporization within the carburetor can cause "a temperature reduction 'of the metal'parts ofythe carburetor up to 50 F. below that of the entering air. Consequently, priorto the time of complete'engine-andradiator warm-up, this drop in temperature may cause formation of ice in the carburetor. Ice'formation probably occurs most readily under conditions of light 'loadjoperation, The result is that after a period of light load operation, when the throttle is closed to the idle position, ice already formedon the throttle plate and adjacent walls, lplus ice which then forms, restricts'the narrow air, openings to cause engine stalling.

To more clearly define the problem of engine stalling due to carburetor icing, data-were, tabulated based on customer'rea'ction surveys, carefully controlled road tests, and laboratory :cold room engine performance tests. These tests show thatcarburetor icing depends primarily uponatmospheric temperature and humidity conditions.

The tests show that stalling difficulties due to ice formation in the carburetor are not encountered below about 30 F., nor above about 60 F. when employing fuels having conventional volatility characteristics. Similarly, these tests demonstrate that stalling is only encountered when the humidity is in excess of about 65%.

Another factor having a bearing on the formation of ice in the carburetor. is the volatility of the fuel employed. To determine this effect laboratory cold room tests were conducted to evaluate the stalling characteristics during warmup of a number of fuels varying in volatility. In these tests a 1947 Chrysler car was installed in a room equipped with temperature and humidity controls. While the temperature and humidity were maintained at particular levels, the stalling characteristics of the car were determined during the warm-up period. The procedure employed was to start the car and to then immediately raise the engine speed to 1500 R. P. M. This speed was maintained for 30 seconds, after which the engine was allowed to idle for 15 seconds. If the engine stalled before 15 seconds had expired, the car was again, istarted and raised to a speed of 1500 R. P. M. for 30 seconds, while if stalling did not occur, the speed was immediately increased to 1500 R. P. M. after the 15 second idling time. The alternate cycles of 30 seconds at 1500 R. P. M. followed by 15 secends at idling were repeated until the engine was completely warmed up. The number of stalls encountered during this procedure, and up to the time of complete engine warm-up were then recorded. Tests were conducted at 40 F. and at a relative humidity of 100% employing three fuels of varying volatilities. The most volatile fuel was a premium grade of commercial gasoline having a A. S. T. M. distillation point of 110 F., a 50% point of 190 F., and a 90% point of 294 F. It was found that this fuel resulted in about 14 or 15 stalls during warm-up. A medium volatility fuel was also tested, consisting of a regular grade commercial gasoline having A. S. T. M. distillation characteristics such that 10% distilled at 121 F., 50% distilled at 220 F., and 90% distilled at 342 F. The number of stalls encountered with this fuel were 11. Finally a low volatility gasoline was subjected to the same test procedure. The gasoline had A. S. T. M..disti11ation 10, 50, and 90% points, at 126 F., 270 F., and 387 F. It was found that 5 stalls were encountered with this fuel.

As indicated by these data, carburetor icing is related to the volatility of the fuel employed. Thus, the least volatile fuel tested above, having a 50% distillation point of 270, only resulted in 5 stalls, while the highest volatility fuel, having a 50% distillation point of 190 F., resulted in 15 stalls. Extrapolating these data as to the volatility of the fuel, it appears that a fuel having a volatility such that the A. S. T. M. 50% distillation point is 310 F., or higher would not be subject to stalling difficulties during warmup. It must be appreciated, however, that a fuel having A. S. T. M. distillation characteristics of this nature would not be desirable as regards warm-up time, cold engine acceleration, economy and crank case dilution. However, in appreciating the scope of the present invention, it is important to note that this invention is only of application to gasoline fuels having an A. S.

T. M. 50% distillation point below about 310 F. At the same time, as will bebrought out, it is possible to corre1ate the quantity of additives required to overcome icing problems with the volatility of the fuel to be improved. In other words, smaller proportions of additives may be employed with fuels of relatively low volatility, while higher proportions of additives may be required with fuels of higher volatility.

It has now been discovered that distinct operating conditions are secured with respect to stalling providing a relatively small critical amount of an aliphatic thioether of a mono-carboxylic acid be utilized. The preferred monocarboxylic acid is selected from the class consisting of acetic acid, propionic acid and butyric acid. Especially desirable compounds are those represented by the formula CxH2x+1-S(CH2)2JCOOH wherein at represents an integer from 8 to 24 and wherein y represents an integer from 1 to 3, as for example, decyl, lauryl, 2-ethylhexyl, tetradecyl, cetyl and stearyl mercaptoacetic acids and mercaptopropionic acids.

The amount of the aliphatic thioether of a monocarboxylic acid employed should be appreciably less than about 1% by volume based upon the volume of gasoline present. The preferred concentration is in the range from about .05% to .5%, especially in the range from about .1 to 3% by volume. v

The compounds of the present invention when employed in motor fuels, as for example, boiling below about 450 are particularly effective when used in conjunction with various esters. Esters which are suitable for combining with the compounds of the present invention, as hereinbefore described, preferably include the esters, or partial esters, of common polyhydric alcohols and any suitable organic acid. Apparently the esters of any suitable polyhydric alcohol and any suitable acid may be used with satisfactory results. For example, the esters of ethylene and polyethylene glycol, glycerol and the like formed with higher acids such as oleic acid, ricinoleic acid, naphthenic acids, and other related compounds of the same general character are quite satisfactory. Ricinoleic acid, which is a major constituent of castor oil, has been found to be quite satisfactory for this purpose.

Other esters than those listed above may be used if desired. For example, the monooleate or dioleate of pentaerythritol and. various analogous derivatives of sorbitol may be employed. Further specific examples are sorbitan monolaurate (sorbitan being a partially dehydrated sorbitol), sorbitan mono-palmitate, or the corresponding monostearate, monooleate, or trioleate, ester, or the polyoxyalkalene' derivatives of any of these sorbitol esters.

The above esters may be employed in a concentration preferably less than about 1% by volume based upon the volume of gasoline present. The preferred concentration is in the range from about .05 to 5%, especially in the range from about .1 to 3% by volume.

The present invention may be more fully understood by the following examples illustrating the same.

Example 1 Motor gasolines containing the addition agents of the present invention were tested by the Simulated Carburetor Icing Test. This test is conducted as follows:

SIMULATED CARBURETOR ICING TESTS 500 ml. of gasoline is cooled to about 10 C. in a Dry Ice-acetone bath and then added to an .Blendor) Oster Mixer (similar in design to a Waring After the gasoline is warmed to above C'. by the mixer chamber, 100 ml. of distilled water is added and while stirring, the temperature is adjusted to exactly C. by the addition of small pieces of Dry Ice. A tall-form polished stainless steel beaker of about 400 ml. capacity which was previously immersed in the gasoline is inserted in the top of the mixer so the bottom of the beaker was about 1 /2" below the top of the mixing chamber. While stirring, 100 m1. of acetone (at room temp.) was added to the beaker and after one minute, 50 grams of pulverized Dry Ice was added to the acetone in the beaker. Power was shut 01f after one minute and the exterior of the beaker was examined to determine the extent of ice deposition caused by the freezing mixture. The results of a series of experiments is given in Table I.

TABLE I WARING BLENDOR CARBURETOR ICING TESTS From the above it is apparent that excellent results are obtained when utilizing the aliphatic thioethers of monocarboxylic acids and that particularly fine results are secured when these thioethers are used in conjunction with various esters.

What is claimed is:

1. A composition comprising a mixture of hydrocarbons boiling in the gasoline boiling range containing from about .05 to 1% by volume of an aliphatic thioether of a mono-carboxylic acid which is selected from the class of compounds represented by the formula wherein :1: represents an integer from 8 to 25 and y represents an integer from 1 to 3 and from about .05 to 1% by volume of an ester selected from the class consisting of a polyhydric alcohol and a higher fatty acid. and a polyhydric alcohol and a naphthenic acid.

4. Composition as defined by claim 3 wherein said thioether comprises lauryl mercaptoacetic acid and said ester comprises polyethylene glycol ditriricinoleate.

ALLEN R. JONES. JOHN 0. SMITH, J'R.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,995,615 Jaeger Mar. 26, 1935 2,073,841 Humphreys et al. Mar. 16, 1937 2,268,382 Clowd Dec. 30, 1941 2,477,356 Wayo July 26, 1949 

1. A COMPOSITION COMPRISING A MIXTURE OF HYDROCARBONS BOILING IN THE GASOLINE BOILING RANGE CONTAINING FROM ABOUT .05 TO 1% BY VOLUME OF AN ALIPHATIC THIOETHER OF A MONO-CARBOXYLIC ACID WHICH IS SELECTED FROM THE CLASS OF COMPOUNDS REPRESENTED BY THE FORMULA 